Hydraulic control device

ABSTRACT

A hydraulic control device for rotating a cam shaft of an internal combustion engine has a sprocket wheel driven by an internal combustion engine, a couple member engageable with a cam shaft and supported by one end of the sprocket wheel and engaging in a central bore hole of the sprocket wheel, a magnet valve arranged so that the couple member is axially displaceable by a liquid pressure controlled by the magnet valve to bring about a relative rotation of the cam shaft relative to the sprocket wheel, and a main piston acting on the couple member and arranged so that the liquid pressure acts on the main piston. A hydraulic body is mounted on the drive wheel, and an axial piston pump is arranged in the hydraulic body and has axial bore holes and a plurality of additional pistons which slide in the bore holes and having outer rounded portions which contact a wobble plate. Outlet valves are arranged at an outlet side of the bore holes and connected to a pressure space defined by the main piston. The main piston and the couple member are arranged so that an element providing a mechanical force acting against a force of the main piston acts on the couple member.

BACKGROUND OF THE INVENTION

The present invention relates to a hydraulic control device for rotatinga cam shaft of an internal combustion engine.

More particularly it relates to a hydraulic control device which has acouple member which is longitudinally displaceable by pressure force andhas a first toothing engaging a toothing at an inner circumference of acam shaft and supported in a sprocket wheel driven by the internalcombustion engine and a second toothing engaging with an inner toothingof a sprocket wheel bore, wherein the couple member is actuallydisplaceable by a liquid pressure controlled by a magnet valve.

Hydraulic control devices of the above-mentioned general type are knownin the art. One such hydraulic control device is disclosed in the Germanpatent document DE-OS 32 47 916. In such a known control device inparticular the pump and the magnet valve are arranged externally, whichis relatively complicated particularly in view of the necessary pressuremedium connections and also entails a considerable cost in construction.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide ahydraulic control device of the above-mentioned type, which avoids thedisadvantages of the prior art.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in a hydraulic control device for rotating a cam shaft of aninternal combustion engine, in which the liquid pressure acts on apiston acting on the couple member, in that a hydraulic body is flangedon at the drive wheel to which the cam shaft is also connected, an axialpiston pump being arranged in the hydraulic member and receiving aplurality of pistons which slide in axial bore holes and have outerrounded portions contacting a wobble plate, outer valves are arranged atthe outlet side of the bore holes and connected to a pressure spacedefined by the piston and controlled by a magnet valve, and a mechanicalforce acting against the force of the piston acts on the couple member.

When the hydraulic control device is designed in accordance with thepresent invention, it has the advantage over the prior art of a verycompact construction and a very simple installation in an internalcombustion engine or its engine compartment.

In accordance with another feature of the present invention, the boreholes receiving the pistons slide in pump bodies which are formed inaxially extending bore holes of the hydraulic body and extendconcentrically to each longitudinal axis. The pump bodies can haveweb-like prolongations by which they dip into recesses of the wobbleplate.

An intermediate part can be connected between the cam shaft and thesprocket wheel and have a continuation which dips into a longitudinalbore hole of the cam shaft, while the spur toothing can be formed at aninner periphery. The cam shaft can be provided with a widened,flange-like end adjoined by the intermediate part and, coaxially theretothe sprocket wheel and the hydraulic body, and these parts can beconnected by screws.

In accordance with still another feature of the present invention, theelectromagnetic valve can be arranged coaxially relative to thehydraulic body and located partially within the same. The hydraulic bodycan include two parts, namely a first body directly adjoining thesprocket wheel and connected to at least one pump body held by a screwpenetrating the widened end part of the cam shaft.

The mechanical force can be generated by a spring, or by a spiraltoothing on the couple member whose pitch angle can be approximately30°-45°.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal section of a first embodiment example of ahydraulic control device for rotating the camshaft of an internalcombustion engine;

FIG. 2 shows a modification of this embodiment example; and

FIG. 3 shows a detail.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the drawing, the camshaft of an internal engine combustion engine isdesignated by 10 and is supported in the camshaft bearing block 11 ofthe internal combustion engine. The camshaft has a continuouslongitudinal bore 12. The sleeve-shaped continuation 13 of a flange part14 which is constructed roughly in the shape of a bowl projects intothis longitudinal bore 12. A sprocket wheel 15 for driving the camshaft12 is connected to the front face of the flange part, followed by acylindrical hydraulic body (main housing) 16. The parts 12 to 16 areheld together so as to be fixed with respect to relative rotation byscrews 17. The above-mentioned parts form an internal hollow space 18 inwhich a couple member or coupling member 20 is arranged. This couplemember 20 has a shaft 21 which projects into the continuation 13 of theflange part 14. A radial or spur toothing or gear teeth 22 isconstructed at the outer circumference of the shaft 21 and engages withan identical spur toothing or gear teeth 23 at the inner circumferenceof the sleeve-shaped continuation. This is followed by a bowl-shapedring part 24 as integral part on the shaft 21 of the couple member 20.The ring part 24 has an inclined or spiral toothing or gear teeth 25 atits outer circumference which engages with an identical spiral toothingor gear teeth 26 at the inner circumference of the sprocket wheel 15. Apiston 29 having constant contact with the base 30 of the couple memberdips into the hollow 28 of the couple member or its ring part 24. Thepiston 29 is supported in a central, continuous bore hole 31 of thehydraulic body 16 and defines a pressure space 32 therein. A deep,axially extending annular groove 34 is formed in the ring part 24 of thecouple member 20. A pressure spring 35 which is supported at the base ofthe flange part 14 and constantly brings the couple member 20 intocontact With the piston 29 is arranged in the annular groove 34.

A plurality of axially extending bore holes 36 are constructed in thehydraulic body 16 in an eccentric, but concentric manner. Pump bodies(pump housings) 37 which receive pistons 39 in their bore holes 38 arearranged in these axially extending bore holes 36. The rounded portionsof these pistons 39 are supported on an inclined wobble plate 40 whichcontacts a diagonally extending, annular crosspiece surface 41 of astationary plate 42. It is evident from this that it is an axial pistonpump 43. Every pump body 37 has two web-like continuations 44, 45 whichproject into corresponding recesses 46, 47 of the wobble plate 40. Thuswhen the hydraulic body 16 rotates when driven by the sprocket wheel 15,the wobble plate 40 also executes a gyrating or wobbling rotationalmovement. Lubricating grooves, not shown in more detail, are advisablyconstructed at the crosspiece surface 41.

A bore hole 49 of small diameter adjoins the bore hole 38 receiving thepiston 39, an outlet valve 50 being arranged in this bore hole 49. Theconstruction of this outlet valve 50 is conventional and therefore notdiscussed in more detail. A duct 51 leads from a location behind theoutlet valve into a pressure space 32.

An annular groove 53 opens out at the piston bore hole 38. A transversehole 54 which is arranged in the pump body 37 opens into this annulargroove 53 and again into a longitudinal groove 55 lying at the outercircumference of the pump body and adjoining the hydraulic body 16. Thelongitudinal groove 55 in turn opens into an angled duct 56 whichcommunicates with an annular space 57 in the hydraulic body 16. Thespiral toothing 25, 26 and an adjoining duct 58 form the connection fromthe annular space 57 to the spur toothing 22, 23 at the couple member20. An annular groove 59 is constructed at the inner circumference ofthe continuation 13 of the flange part 14. A transverse bore 60 which isarranged in the camshaft 10 and is in turn connected with a transversebore hole 61 in the camshaft bearing block 11 opens into the annulargroove 59. The transverse bore hole 61 is connected with an oilreceptacle 63 via a bore hole 62 constructed in the cylinder head.

A magnet valve 65 which operates in a flow-proportional manner andaccordingly forms a proportional pressure control valve adjoins thepressure space 32. This magnet valve 65 has a coil 66 which is arrangedin a coil body 67 and simultaneously forms a cover 68. The armature 69in which a tappet 70 is securely arranged is located inside the coilbody 67. This tappet 70 slides in a pole plate 71 which is turn contactsa plate 72 closing the bore hole 31. A continuous bore hole 73 isconstructed in this plate 72 and is controlled by the spherical valvebody 74 of the electromagnetic valve 65 and is actuated by the tappet70. A transversely extending duct 77--thus arranged at the output of theelectromagnetic valve--is located between the plate 72 and pole plate 61and opens into the recess 78 in the hydraulic body 16. There is also aconnection from the space 79 situated in the latter to the receptacle63. Additional bore holes and ducts, not shown, e.g. in the shaft 21 ofthe couple member, have no bearing on the present invention.

It should also be noted that the pump bodies 37 are secured by screws 76which penetrate the flange part 14, the sprocket wheel 15 and thehydraulic body 16. Bushes 75 which lie in corresponding curved slots 75Aof the sprocket wheel are arranged at the locations where the screws 17,76 traverse the sprocket wheel and are penetrated by these screws sothat the camshaft 10 can be rotated relative to the sprocket wheel 15.

The hydraulic control device operates in the following manner: when thecamshaft 10 is set in rotation by the sprocket wheel 15, the flange part14 and the hydraulic body 16 also participate in the rotation. Thepistons 39 of the axial piston pump now execute lifting movements due totheir contact at the wobble plate 40. They suck pressure medium out ofthe receptacle 63 via the following connection: transverse bore holes62, 61, 60, annular groove 59, spur toothing 22, 23, duct 58, spiraltoothing 25, 26, annular space 57 in the hydraulic body 16, duct 56,longitudinal groove 55, transverse hole 54, and annular groove 53 at thepiston bore hole 38.

When no current is applied to the magnet valve 65, the valve body 74 islifted from its valve seat and the pressure medium which is conductedinto the pressure space 32 by the pistons 39 via the outlet valve 50 ispushed out without pressure into the space 79 or the receptacle 63 viathe magnet valve, the transverse bore hole 77 and the recess 78.

The pressure spring 35 slides the couple member 20 to the left (in thedirection of the magnet valve 65) and the camshaft 10 is rotatedrelative to the sprocket wheel 15 via the described teeth. It occupies afirst position. At maximum current to the magnet valve, the valve body74 is pressed on its valve seat by the action of the armature 69 and thetappet 70. At this point, the pressure in the pressure space 32 reachesits maximum value and slides the piston 29 to the right, the latterdisplacing the couple member 20. The camshaft 10 is now rotated relativeto the sprocket wheel 15 into a second position due to the teethdescribed above. At partial current to the magnet valve, the couplemember, and accordingly also the camshaft, can be brought into optionalintermediate positions.

The embodiment example according to FIG. 2 differs from the previousembodiment example substantially in that the hydraulic body isconstructed somewhat differently. It now has two parts 80, 81, one ofwhich 81 directly adjoins the camshaft and is screwed together with thelatter. The part so--designated here as pump body--is likewise screwedto the camshaft. (However, in this instance the screws are arrangeddifferently, but this is not at all essential to the invention.)

The pump body 80 is not constructed so as to be symmetrical with respectto rotation and includes a sleeve which--as described above--is screwedtogether With the camshaft. The pump body is discussed only brieflysince its construction is extensively identical to that of the precedingembodiment example. Identical parts are provided with the same referencenumbers. The difference here consists in the manner in which thepressure medium is conveyed to and away from the pump body.

A spring disk 82 is arranged between the pump body 80 and the part 81 asis shown in FIG. 3 in a top view. It simultaneously forms the outletvalve in the form of a spring tongue 83 which is enlarged 84 at its endcontacting the outlet bore hole 85 of the piston bore hole 86. Thespring disk is held by a positioning pin which is not shown in greaterdetail. A bore hole 87A is also located in the spring plate. The suctionbore hole 87 in which is arranged a suction throttle 88 connected withhole 87A in the spring plate 82 extends in the pump body 80. The suctionbore hole 87 leads up to the space 57 which is connected with thepressure medium reservoir. The outlet bore hole 85 is connected to thepressure space 32 via a duct 89. For easy mounting of the pump body orpump bodies 80, a wire clasp 91 is provided which fixes the wobble platewith the piston pump acted upon by spring pressure in the preassembledadjusting unit. This is not discussed in greater detail.

The electromagnetic valve 93 is also slightly modified compared to theembodiment example in FIG. 1. In addition to the armature 69, alongitudinal groove 95 is constructed in the coil body 94. Accordingly,eddy currents which exert a deceleration moment on the armature areinduced in the excited electromagnetic valve during the rotation of thecamshaft and armature. The suspension of the armature at the tappet 70and the transmission of force to the valve body 74 allow the rotation ofthe armature and magnet core. The rotating tappet exhibits virtually nofrictional force during axial movement. The electromagnetic valveaccordingly has low hysteresis so that the pressure in the pressurespace 32 can be adjusted in a particularly exact manner.

Voltage can also be applied to the magnet valves described in the twoembodiment examples at a frequency of roughly 100 Hertz and a variableduty ratio. Duty ratio is understood as the ratio of supplied currentduration of the electromagnets to the total period of applied voltage.At a low duty ratio, the magnet valve is only closed briefly. Theopening cross section averaged over time drops with the duty ratio.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in ahydraulic control device, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:
 1. A hydraulic control device forrotating a cam shaft of an internal combustion engine, comprising ahollow-cylindrical sprocket wheel driven by an internal combustionengine and having a central bore hole with a set of gear teeth at itsinner circumference; a coupling member longitudinally displaceable by ahydraulic pressure and having a first location on an outer circumferenceof the coupling member provided with a first set of gear teethengageable with a set of gear teeth located at an inner circumference ofsaid cam shaft, and a second location provided on the outercircumference of the coupling member having a second set of gear teethengaging with said set of gear teeth at the inner circumference of saidcentral bore hole of said sprocket wheel, so as to form two gear teethpairs, one of said gear teeth pairs constituting spiral gear teeth andthe other of said gear teeth pairs constituting spur gear teeth; anelectromagnetic valve arranged so that said coupling member is axiallydisplaced by said hydraulic pressure controlled by said electromagneticvalve so as to bring about a relative rotation of said cam shaftrelative to said sprocket wheel; a main piston acting on said couplingmember and arranged so that said hydraulic pressure acts on said mainpiston; a main housing mounted on said drive wheel to which said camshaft is also connectable; an axial piston pump connected to said mainhousing having axial bore holes being substantially parallel to acentral axis of said cam shaft, and a plurality of additional pistonswhich are located in said axial bore holes; each piston having an outerrounded portion which contacts a wobble plate; outlet valves arranged atan outlet side of said bore holes and connected to a pressure space inthe pump housing adjacent said main piston, said electromagnetic valvecontrols the hydraulic pump by controlling a pressure in said pressurespace, said main piston and said coupling member arranged so that amechanical force providing means acts on said coupling member against aforce on said main piston.
 2. A hydraulic control device as defined inclaim 1, and further comprising pump housings which are formed in axialbore holes of said main housing and extend concentrically to alongitudinal axis of said main housing, said bore holes receiving saidadditional pistons sliding in said pump housings.
 3. A hydraulic controldevice as defined in claim 2, wherein said wobble plate has recesses,said pump housings having web-like prolongations dipping into saidrecesses of said wobble plate.
 4. A hydraulic control device as definedin claim 1, and further comprising an intermediate part located betweenthe cam shaft and said sprocket wheel and having a continuationinsertable into a longitudinal bore hole of the cam shaft, said spurgear teeth being formed at an inner circumference of said continuation.5. A hydraulic control device as defined in claim 4, and furthercomprising a widened flange-like end part provided on the cam shaft,said intermediate part adjoining said end part, said sprocket wheel andsaid hydraulic body being located coaxially relative to saidintermediate part; and further comprising a means for connecting saidintermediate part, said sprocket wheel and said hydraulic body with oneanother.
 6. A hydraulic control device as defined in claim 5, whereinsaid connecting means are formed as screws.
 7. A hydraulic controldevice as defined in claim 1 wherein said electromagnetic valve isarranged coaxially relative to said main housing and is locatedpartially in said main housing.
 8. A hydraulic control device as definedin claim 1, wherein said main housing includes a first housing whichdirectly adjoins said sprocket wheel and at least one pump housingconnected to said first housing with said first housing and including ascrew extending through a part of the cam shaft, said sprocket wheel andsaid first housing; and a spring disk type outlet valve arranged betweensaid pump housing and said first housing and having a tongue-like valvepart with an enlargement located at an outlet.
 9. A hydraulic controldevice as defined in claim 1, wherein said electromagnetic valve has anarmature and a coil body which receives the armature and has alongitudinal groove.
 10. A hydraulic control device as defined in claim1, wherein said mechanical force providing means is formed as a spring.11. A hydraulic control device as defined in claim 1, wherein saidspiral gear teeth have a pitch angle substantially between 30° and 45°.